Yup. And using a repeater colors this as well. You can be getting a strong signal from the repeater from an operator who is barely breaking the squelch of the repeater and thus R1 or worse with an S9 (because the Rx comes from the other operator's input to the repeater, and the Sx comes from your input from the repeater). Or you can be the one on the fringe of the repeater's range, hearing a solid operator into the repeater but you hear R1/S1.

It's much easier to determine the reason for a specific signal report
operating simplex.

There's no reason to report signal strength on a repeater, no one really cares that you have S9 from a repeater. It seems that most people just ask how they are getting into the repeater, so I suppose you could report an R number. Most people seem to just say you are either getting into a repeater or not. Of course you know that you get broke the squelch on a repeater if you hear the tail after unkeying your mic, so you get that immediate ack. But yeah, really RST is a simplex tool.